1. Field of the Invention
The present invention relates to a metal complex solution, to a photosensitive metal complex solution, and to a method for forming metallic oxide films (including patterned metallic oxide films).
2. Background Art
Metallic oxides have attracted attention from old times due to their thermal, optical, electrical, magnetic and mechanical properties, and conventionally have been applied to various uses in the field of industry. Especially in the field of recent electronic materials, transparent conducting films are used as antistatic materials, materials for heat ray cut-off filters, materials for ultraviolet light cut-off filters, magnetic-wave-shielding materials, materials for transparent electrodes to be used for liquid crystal displays, plasma displays, etc., and materials for producing deicing heaters to be used for window glasses, etc. Further, a variety of metallic oxide films are utilized for those uses which require neither transparency nor electrical conductivity.
Indium oxide/tin oxide (ITO) films have been known as being typical of the above-described transparent conducting films. These metallic oxides can readily form transparent films on glass or ceramic substrates to give transparent conducting films. As methods for forming such transparent conducting films, there have been known, for example, the sputtering process and the sol-gel process. Further, for those uses which require neither transparency nor electrical conductivity, a variety of metallic oxide films are formed by these processes.
The above-described conventional sputtering process is disadvantageous from the view points of production cost and mass-productivity because the film deposition system for use in this process is complicated and also expensive. In order to solve these problems, there have been proposed various methods of application utilizing the so-called sol-gel process, typically a method as described, for example, in Japanese Patent Publication No. 46402/1991. However, those metallic oxide films, especially transparent conducting films which are formed by these methods of application are still insufficient in their qualities. Namely, there are such practical problems that the qualities of the metallic oxide films are unsatisfactory and that, since the transparent conducting films formed have high electrical resistance, they cannot be used for electrodes or the like to be used for display elements, etc. when electrical conductivity is taken into consideration.
Further, as a method for forming patterns in the above-described metallic oxide films or transparent conducting films, there has been known a so-called photolithographic method which comprises a series of complicated steps of providing a resist layer on a metallic oxide film or transparent conducting film formed by the aforementioned sputtering or sol-gel process, subjecting the resist layer to mask-pattern-wise exposure and to development, etching the metallic oxide film or transparent conducting film, and removing the resist layer.
The above-described conventional method for forming patterned metallic oxide films or transparent conducting films is a complicated and long process consisting of two film-forming steps of forming a metallic oxide film or transparent conducting film and a resist layer, one step of exposure, and three wet chemical conversion treatment steps of developing the resist layer, removing the same, and etching the metallic oxide film or transparent conducting film. This method is thus disadvantageous when considering production cost and non-defective rate.
An object of the present invention is therefore to provide a metal complex solution or photosensitive metal complex solution with which a high-quality metallic oxide film, or a transparent conducting film, such as an ITO film, having low electrical resistance and high transparency can be formed on a substrate by the above-described method of application utilizing the so-called sol-gel process, and to provide a method for forming metallic oxide films.
In order to attain the foregoing object, the present invention provides a metal complex solution comprising an organic solvent, and a complex composed of an organic acid salt of at least one metal and an organic amine or organic ketone compound, dissolved in the organic solvent; and a photosensitive metal complex solution comprising the metal complex solution, and a photosensitive resin added thereto. Further, the present invention provides a method for forming a metallic oxide film, comprising the steps of coating the above-described metal complex solution onto a heat-resistant substrate, drying the coating to form a film, and heat-treating the film to obtain a metallic oxide film. Furthermore, the present invention also provides a method for forming patterned metallic oxide film, comprising the steps of coating the above-described photosensitive metal complex solution onto a heat-resistant substrate, drying the coating to form a film, subjecting the film to pattern-wise exposure, and developing the exposed film.
According to the present invention, it becomes possible to form high-quality metallic oxide films, or transparent conducting films, such as ITO films, having low electrical resistance and high transparency on substrates by a method of application utilizing the so-called sol-gel process.